[Linuxconsole-commit] SF.net SVN: linuxconsole: [2371] branches/ruby-2.6.21/ruby-2.6/drivers/char /tty_io.c

[<jsi...@us...>]

Revision: 2371
          http://linuxconsole.svn.sourceforge.net/linuxconsole/?rev=2371&view=rev
Author:   jsimmons
Date:     2007-04-11 12:53:20 -0700 (Wed, 11 Apr 2007)

Log Message:
-----------
updated to tty_io

Modified Paths:
--------------
    branches/ruby-2.6.21/ruby-2.6/drivers/char/tty_io.c

Modified: branches/ruby-2.6.21/ruby-2.6/drivers/char/tty_io.c
===================================================================
--- branches/ruby-2.6.21/ruby-2.6/drivers/char/tty_io.c	2007-04-11 19:49:18 UTC (rev 2370)
+++ branches/ruby-2.6.21/ruby-2.6/drivers/char/tty_io.c	2007-04-11 19:53:20 UTC (rev 2371)
@@ -65,7 +65,6 @@
  * alloc_tty_struct() always uses kmalloc() -- Andrew Morton <an...@uo...> 17Mar01
  */
 
-#include <linux/config.h>
 #include <linux/types.h>
 #include <linux/major.h>
 #include <linux/errno.h>
@@ -93,12 +92,12 @@
 #include <linux/idr.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
+#include <linux/delay.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
 
 #include <linux/vt_kern.h>
-#include <linux/devfs_fs_kernel.h>
 
 #include <linux/kmod.h>
 
@@ -107,13 +106,15 @@
 #define TTY_PARANOIA_CHECK 1
 #define CHECK_TTY_COUNT 1
 
-struct termios tty_std_termios = {	/* for the benefit of tty drivers  */
+struct ktermios tty_std_termios = {	/* for the benefit of tty drivers  */
 	.c_iflag = ICRNL | IXON,
 	.c_oflag = OPOST | ONLCR,
 	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
 	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
 		   ECHOCTL | ECHOKE | IEXTEN,
-	.c_cc = INIT_C_CC
+	.c_cc = INIT_C_CC,
+	.c_ispeed = 38400,
+	.c_ospeed = 38400
 };
 
 EXPORT_SYMBOL(tty_std_termios);
@@ -124,9 +125,10 @@
    
 LIST_HEAD(tty_drivers);			/* linked list of tty drivers */
 
-/* Semaphore to protect creating and releasing a tty. This is shared with
+/* Mutex to protect creating and releasing a tty. This is shared with
    vt.c for deeply disgusting hack reasons */
-DECLARE_MUTEX(tty_sem);
+DEFINE_MUTEX(tty_mutex);
+EXPORT_SYMBOL(tty_mutex);
 
 #ifdef CONFIG_UNIX98_PTYS
 extern struct tty_driver *ptm_driver;	/* Unix98 pty masters; for /dev/ptmx */
@@ -149,28 +151,55 @@
 int tty_ioctl(struct inode * inode, struct file * file,
 	      unsigned int cmd, unsigned long arg);
 static int tty_fasync(int fd, struct file * filp, int on);
-extern void rs_360_init(void);
-static void release_mem(struct tty_struct *tty, int idx);
+static void release_tty(struct tty_struct *tty, int idx);
+static struct pid *__proc_set_tty(struct task_struct *tsk,
+				struct tty_struct *tty);
 
+/**
+ *	alloc_tty_struct	-	allocate a tty object
+ *
+ *	Return a new empty tty structure. The data fields have not
+ *	been initialized in any way but has been zeroed
+ *
+ *	Locking: none
+ */
 
 static struct tty_struct *alloc_tty_struct(void)
 {
-	struct tty_struct *tty;
-
-	tty = kmalloc(sizeof(struct tty_struct), GFP_KERNEL);
-	if (tty)
-		memset(tty, 0, sizeof(struct tty_struct));
-	return tty;
+	return kzalloc(sizeof(struct tty_struct), GFP_KERNEL);
 }
 
+static void tty_buffer_free_all(struct tty_struct *);
+
+/**
+ *	free_tty_struct		-	free a disused tty
+ *	@tty: tty struct to free
+ *
+ *	Free the write buffers, tty queue and tty memory itself.
+ *
+ *	Locking: none. Must be called after tty is definitely unused
+ */
+
 static inline void free_tty_struct(struct tty_struct *tty)
 {
 	kfree(tty->write_buf);
+	tty_buffer_free_all(tty);
 	kfree(tty);
 }
 
 #define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)
 
+/**
+ *	tty_name	-	return tty naming
+ *	@tty: tty structure
+ *	@buf: buffer for output
+ *
+ *	Convert a tty structure into a name. The name reflects the kernel
+ *	naming policy and if udev is in use may not reflect user space
+ *
+ *	Locking: none
+ */
+
 char *tty_name(struct tty_struct *tty, char *buf)
 {
 	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
@@ -222,22 +251,366 @@
 				    "!= #fd's(%d) in %s\n",
 		       tty->name, tty->count, count, routine);
 		return count;
-       }	
+	}
 #endif
 	return 0;
 }
 
 /*
+ * Tty buffer allocation management
+ */
+
+/**
+ *	tty_buffer_free_all		-	free buffers used by a tty
+ *	@tty: tty to free from
+ *
+ *	Remove all the buffers pending on a tty whether queued with data
+ *	or in the free ring. Must be called when the tty is no longer in use
+ *
+ *	Locking: none
+ */
+
+static void tty_buffer_free_all(struct tty_struct *tty)
+{
+	struct tty_buffer *thead;
+	while((thead = tty->buf.head) != NULL) {
+		tty->buf.head = thead->next;
+		kfree(thead);
+	}
+	while((thead = tty->buf.free) != NULL) {
+		tty->buf.free = thead->next;
+		kfree(thead);
+	}
+	tty->buf.tail = NULL;
+	tty->buf.memory_used = 0;
+}
+
+/**
+ *	tty_buffer_init		-	prepare a tty buffer structure
+ *	@tty: tty to initialise
+ *
+ *	Set up the initial state of the buffer management for a tty device.
+ *	Must be called before the other tty buffer functions are used.
+ *
+ *	Locking: none
+ */
+
+static void tty_buffer_init(struct tty_struct *tty)
+{
+	spin_lock_init(&tty->buf.lock);
+	tty->buf.head = NULL;
+	tty->buf.tail = NULL;
+	tty->buf.free = NULL;
+	tty->buf.memory_used = 0;
+}
+
+/**
+ *	tty_buffer_alloc	-	allocate a tty buffer
+ *	@tty: tty device
+ *	@size: desired size (characters)
+ *
+ *	Allocate a new tty buffer to hold the desired number of characters.
+ *	Return NULL if out of memory or the allocation would exceed the
+ *	per device queue
+ *
+ *	Locking: Caller must hold tty->buf.lock
+ */
+
+static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
+{
+	struct tty_buffer *p;
+
+	if (tty->buf.memory_used + size > 65536)
+		return NULL;
+	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
+	if(p == NULL)
+		return NULL;
+	p->used = 0;
+	p->size = size;
+	p->next = NULL;
+	p->commit = 0;
+	p->read = 0;
+	p->char_buf_ptr = (char *)(p->data);
+	p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
+	tty->buf.memory_used += size;
+	return p;
+}
+
+/**
+ *	tty_buffer_free		-	free a tty buffer
+ *	@tty: tty owning the buffer
+ *	@b: the buffer to free
+ *
+ *	Free a tty buffer, or add it to the free list according to our
+ *	internal strategy
+ *
+ *	Locking: Caller must hold tty->buf.lock
+ */
+
+static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
+{
+	/* Dumb strategy for now - should keep some stats */
+	tty->buf.memory_used -= b->size;
+	WARN_ON(tty->buf.memory_used < 0);
+
+	if(b->size >= 512)
+		kfree(b);
+	else {
+		b->next = tty->buf.free;
+		tty->buf.free = b;
+	}
+}
+
+/**
+ *	tty_buffer_find		-	find a free tty buffer
+ *	@tty: tty owning the buffer
+ *	@size: characters wanted
+ *
+ *	Locate an existing suitable tty buffer or if we are lacking one then
+ *	allocate a new one. We round our buffers off in 256 character chunks
+ *	to get better allocation behaviour.
+ *
+ *	Locking: Caller must hold tty->buf.lock
+ */
+
+static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
+{
+	struct tty_buffer **tbh = &tty->buf.free;
+	while((*tbh) != NULL) {
+		struct tty_buffer *t = *tbh;
+		if(t->size >= size) {
+			*tbh = t->next;
+			t->next = NULL;
+			t->used = 0;
+			t->commit = 0;
+			t->read = 0;
+			tty->buf.memory_used += t->size;
+			return t;
+		}
+		tbh = &((*tbh)->next);
+	}
+	/* Round the buffer size out */
+	size = (size + 0xFF) & ~ 0xFF;
+	return tty_buffer_alloc(tty, size);
+	/* Should possibly check if this fails for the largest buffer we
+	   have queued and recycle that ? */
+}
+
+/**
+ *	tty_buffer_request_room		-	grow tty buffer if needed
+ *	@tty: tty structure
+ *	@size: size desired
+ *
+ *	Make at least size bytes of linear space available for the tty
+ *	buffer. If we fail return the size we managed to find.
+ *
+ *	Locking: Takes tty->buf.lock
+ */
+int tty_buffer_request_room(struct tty_struct *tty, size_t size)
+{
+	struct tty_buffer *b, *n;
+	int left;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->buf.lock, flags);
+
+	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
+	   remove this conditional if its worth it. This would be invisible
+	   to the callers */
+	if ((b = tty->buf.tail) != NULL)
+		left = b->size - b->used;
+	else
+		left = 0;
+
+	if (left < size) {
+		/* This is the slow path - looking for new buffers to use */
+		if ((n = tty_buffer_find(tty, size)) != NULL) {
+			if (b != NULL) {
+				b->next = n;
+				b->commit = b->used;
+			} else
+				tty->buf.head = n;
+			tty->buf.tail = n;
+		} else
+			size = left;
+	}
+
+	spin_unlock_irqrestore(&tty->buf.lock, flags);
+	return size;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_request_room);
+
+/**
+ *	tty_insert_flip_string	-	Add characters to the tty buffer
+ *	@tty: tty structure
+ *	@chars: characters
+ *	@size: size
+ *
+ *	Queue a series of bytes to the tty buffering. All the characters
+ *	passed are marked as without error. Returns the number added.
+ *
+ *	Locking: Called functions may take tty->buf.lock
+ */
+
+int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars,
+				size_t size)
+{
+	int copied = 0;
+	do {
+		int space = tty_buffer_request_room(tty, size - copied);
+		struct tty_buffer *tb = tty->buf.tail;
+		/* If there is no space then tb may be NULL */
+		if(unlikely(space == 0))
+			break;
+		memcpy(tb->char_buf_ptr + tb->used, chars, space);
+		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
+		tb->used += space;
+		copied += space;
+		chars += space;
+		/* There is a small chance that we need to split the data over
+		   several buffers. If this is the case we must loop */
+	} while (unlikely(size > copied));
+	return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string);
+
+/**
+ *	tty_insert_flip_string_flags	-	Add characters to the tty buffer
+ *	@tty: tty structure
+ *	@chars: characters
+ *	@flags: flag bytes
+ *	@size: size
+ *
+ *	Queue a series of bytes to the tty buffering. For each character
+ *	the flags array indicates the status of the character. Returns the
+ *	number added.
+ *
+ *	Locking: Called functions may take tty->buf.lock
+ */
+
+int tty_insert_flip_string_flags(struct tty_struct *tty,
+		const unsigned char *chars, const char *flags, size_t size)
+{
+	int copied = 0;
+	do {
+		int space = tty_buffer_request_room(tty, size - copied);
+		struct tty_buffer *tb = tty->buf.tail;
+		/* If there is no space then tb may be NULL */
+		if(unlikely(space == 0))
+			break;
+		memcpy(tb->char_buf_ptr + tb->used, chars, space);
+		memcpy(tb->flag_buf_ptr + tb->used, flags, space);
+		tb->used += space;
+		copied += space;
+		chars += space;
+		flags += space;
+		/* There is a small chance that we need to split the data over
+		   several buffers. If this is the case we must loop */
+	} while (unlikely(size > copied));
+	return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string_flags);
+
+/**
+ *	tty_schedule_flip	-	push characters to ldisc
+ *	@tty: tty to push from
+ *
+ *	Takes any pending buffers and transfers their ownership to the
+ *	ldisc side of the queue. It then schedules those characters for
+ *	processing by the line discipline.
+ *
+ *	Locking: Takes tty->buf.lock
+ */
+
+void tty_schedule_flip(struct tty_struct *tty)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&tty->buf.lock, flags);
+	if (tty->buf.tail != NULL)
+		tty->buf.tail->commit = tty->buf.tail->used;
+	spin_unlock_irqrestore(&tty->buf.lock, flags);
+	schedule_delayed_work(&tty->buf.work, 1);
+}
+EXPORT_SYMBOL(tty_schedule_flip);
+
+/**
+ *	tty_prepare_flip_string		-	make room for characters
+ *	@tty: tty
+ *	@chars: return pointer for character write area
+ *	@size: desired size
+ *
+ *	Prepare a block of space in the buffer for data. Returns the length
+ *	available and buffer pointer to the space which is now allocated and
+ *	accounted for as ready for normal characters. This is used for drivers
+ *	that need their own block copy routines into the buffer. There is no
+ *	guarantee the buffer is a DMA target!
+ *
+ *	Locking: May call functions taking tty->buf.lock
+ */
+
+int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, size_t size)
+{
+	int space = tty_buffer_request_room(tty, size);
+	if (likely(space)) {
+		struct tty_buffer *tb = tty->buf.tail;
+		*chars = tb->char_buf_ptr + tb->used;
+		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
+		tb->used += space;
+	}
+	return space;
+}
+
+EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
+
+/**
+ *	tty_prepare_flip_string_flags	-	make room for characters
+ *	@tty: tty
+ *	@chars: return pointer for character write area
+ *	@flags: return pointer for status flag write area
+ *	@size: desired size
+ *
+ *	Prepare a block of space in the buffer for data. Returns the length
+ *	available and buffer pointer to the space which is now allocated and
+ *	accounted for as ready for characters. This is used for drivers
+ *	that need their own block copy routines into the buffer. There is no
+ *	guarantee the buffer is a DMA target!
+ *
+ *	Locking: May call functions taking tty->buf.lock
+ */
+
+int tty_prepare_flip_string_flags(struct tty_struct *tty, unsigned char **chars, char **flags, size_t size)
+{
+	int space = tty_buffer_request_room(tty, size);
+	if (likely(space)) {
+		struct tty_buffer *tb = tty->buf.tail;
+		*chars = tb->char_buf_ptr + tb->used;
+		*flags = tb->flag_buf_ptr + tb->used;
+		tb->used += space;
+	}
+	return space;
+}
+
+EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
+
+
+
+/**
+ *	tty_set_termios_ldisc		-	set ldisc field
+ *	@tty: tty structure
+ *	@num: line discipline number
+ *
  *	This is probably overkill for real world processors but
  *	they are not on hot paths so a little discipline won't do 
  *	any harm.
+ *
+ *	Locking: takes termios_mutex
  */
  
 static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
 {
-	down(&tty->termios_sem);
+	mutex_lock(&tty->termios_mutex);
 	tty->termios->c_line = num;
-	up(&tty->termios_sem);
+	mutex_unlock(&tty->termios_mutex);
 }
 
 /*
@@ -248,8 +621,21 @@
  
 static DEFINE_SPINLOCK(tty_ldisc_lock);
 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
-static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table	*/
+static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table */
 
+/**
+ *	tty_register_ldisc	-	install a line discipline
+ *	@disc: ldisc number
+ *	@new_ldisc: pointer to the ldisc object
+ *
+ *	Installs a new line discipline into the kernel. The discipline
+ *	is set up as unreferenced and then made available to the kernel
+ *	from this point onwards.
+ *
+ *	Locking:
+ *		takes tty_ldisc_lock to guard against ldisc races
+ */
+
 int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
 {
 	unsigned long flags;
@@ -259,24 +645,60 @@
 		return -EINVAL;
 	
 	spin_lock_irqsave(&tty_ldisc_lock, flags);
-	if (new_ldisc) {
-		tty_ldiscs[disc] = *new_ldisc;
-		tty_ldiscs[disc].num = disc;
-		tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
-		tty_ldiscs[disc].refcount = 0;
-	} else {
-		if(tty_ldiscs[disc].refcount)
-			ret = -EBUSY;
-		else
-			tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
-	}
+	tty_ldiscs[disc] = *new_ldisc;
+	tty_ldiscs[disc].num = disc;
+	tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
+	tty_ldiscs[disc].refcount = 0;
 	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 	
 	return ret;
 }
-
 EXPORT_SYMBOL(tty_register_ldisc);
 
+/**
+ *	tty_unregister_ldisc	-	unload a line discipline
+ *	@disc: ldisc number
+ *	@new_ldisc: pointer to the ldisc object
+ *
+ *	Remove a line discipline from the kernel providing it is not
+ *	currently in use.
+ *
+ *	Locking:
+ *		takes tty_ldisc_lock to guard against ldisc races
+ */
+
+int tty_unregister_ldisc(int disc)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	if (disc < N_TTY || disc >= NR_LDISCS)
+		return -EINVAL;
+
+	spin_lock_irqsave(&tty_ldisc_lock, flags);
+	if (tty_ldiscs[disc].refcount)
+		ret = -EBUSY;
+	else
+		tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
+	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(tty_unregister_ldisc);
+
+/**
+ *	tty_ldisc_get		-	take a reference to an ldisc
+ *	@disc: ldisc number
+ *
+ *	Takes a reference to a line discipline. Deals with refcounts and
+ *	module locking counts. Returns NULL if the discipline is not available.
+ *	Returns a pointer to the discipline and bumps the ref count if it is
+ *	available
+ *
+ *	Locking:
+ *		takes tty_ldisc_lock to guard against ldisc races
+ */
+
 struct tty_ldisc *tty_ldisc_get(int disc)
 {
 	unsigned long flags;
@@ -305,25 +727,47 @@
 
 EXPORT_SYMBOL_GPL(tty_ldisc_get);
 
+/**
+ *	tty_ldisc_put		-	drop ldisc reference
+ *	@disc: ldisc number
+ *
+ *	Drop a reference to a line discipline. Manage refcounts and
+ *	module usage counts
+ *
+ *	Locking:
+ *		takes tty_ldisc_lock to guard against ldisc races
+ */
+
 void tty_ldisc_put(int disc)
 {
 	struct tty_ldisc *ld;
 	unsigned long flags;
 	
-	if (disc < N_TTY || disc >= NR_LDISCS)
-		BUG();
+	BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
 		
 	spin_lock_irqsave(&tty_ldisc_lock, flags);
 	ld = &tty_ldiscs[disc];
-	if(ld->refcount == 0)
-		BUG();
-	ld->refcount --;
+	BUG_ON(ld->refcount == 0);
+	ld->refcount--;
 	module_put(ld->owner);
 	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 }
 	
 EXPORT_SYMBOL_GPL(tty_ldisc_put);
 
+/**
+ *	tty_ldisc_assign	-	set ldisc on a tty
+ *	@tty: tty to assign
+ *	@ld: line discipline
+ *
+ *	Install an instance of a line discipline into a tty structure. The
+ *	ldisc must have a reference count above zero to ensure it remains/
+ *	The tty instance refcount starts at zero.
+ *
+ *	Locking:
+ *		Caller must hold references
+ */
+
 static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
 {
 	tty->ldisc = *ld;
@@ -338,6 +782,8 @@
  *	the tty ldisc. Return 0 on failure or 1 on success. This is
  *	used to implement both the waiting and non waiting versions
  *	of tty_ldisc_ref
+ *
+ *	Locking: takes tty_ldisc_lock
  */
 
 static int tty_ldisc_try(struct tty_struct *tty)
@@ -369,6 +815,8 @@
  *	must also be careful not to hold other locks that will deadlock
  *	against a discipline change, such as an existing ldisc reference
  *	(which we check for)
+ *
+ *	Locking: call functions take tty_ldisc_lock
  */
  
 struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
@@ -389,6 +837,8 @@
  *	Dereference the line discipline for the terminal and take a 
  *	reference to it. If the line discipline is in flux then 
  *	return NULL. Can be called from IRQ and timer functions.
+ *
+ *	Locking: called functions take tty_ldisc_lock
  */
  
 struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
@@ -406,14 +856,15 @@
  *
  *	Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
  *	be called in IRQ context.
+ *
+ *	Locking: takes tty_ldisc_lock
  */
  
 void tty_ldisc_deref(struct tty_ldisc *ld)
 {
 	unsigned long flags;
 
-	if(ld == NULL)
-		BUG();
+	BUG_ON(ld == NULL);
 		
 	spin_lock_irqsave(&tty_ldisc_lock, flags);
 	if(ld->refcount == 0)
@@ -451,25 +902,26 @@
  *
  *	Set the discipline of a tty line. Must be called from a process
  *	context.
+ *
+ *	Locking: takes tty_ldisc_lock.
+ *		 called functions take termios_mutex
  */
  
 static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 {
-	int	retval = 0;
-	struct	tty_ldisc o_ldisc;
+	int retval = 0;
+	struct tty_ldisc o_ldisc;
 	char buf[64];
 	int work;
 	unsigned long flags;
 	struct tty_ldisc *ld;
+	struct tty_struct *o_tty;
 
 	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
 		return -EINVAL;
 
 restart:
 
-	if (tty->ldisc.num == ldisc)
-		return 0;	/* We are already in the desired discipline */
-	
 	ld = tty_ldisc_get(ldisc);
 	/* Eduardo Blanco <ej...@cs...> */
 	/* Cyrus Durgin <ci...@sp...> */
@@ -480,48 +932,85 @@
 	if (ld == NULL)
 		return -EINVAL;
 
-	o_ldisc = tty->ldisc;
+	/*
+	 *	No more input please, we are switching. The new ldisc
+	 *	will update this value in the ldisc open function
+	 */
 
+	tty->receive_room = 0;
+
+	/*
+	 *	Problem: What do we do if this blocks ?
+	 */
+
 	tty_wait_until_sent(tty, 0);
 
+	if (tty->ldisc.num == ldisc) {
+		tty_ldisc_put(ldisc);
+		return 0;
+	}
+
+	o_ldisc = tty->ldisc;
+	o_tty = tty->link;
+
 	/*
 	 *	Make sure we don't change while someone holds a
 	 *	reference to the line discipline. The TTY_LDISC bit
 	 *	prevents anyone taking a reference once it is clear.
 	 *	We need the lock to avoid racing reference takers.
 	 */
-	 
+
 	spin_lock_irqsave(&tty_ldisc_lock, flags);
-	if(tty->ldisc.refcount)
-	{
-		/* Free the new ldisc we grabbed. Must drop the lock
-		   first. */
+	if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
+		if(tty->ldisc.refcount) {
+			/* Free the new ldisc we grabbed. Must drop the lock
+			   first. */
+			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+			tty_ldisc_put(ldisc);
+			/*
+			 * There are several reasons we may be busy, including
+			 * random momentary I/O traffic. We must therefore
+			 * retry. We could distinguish between blocking ops
+			 * and retries if we made tty_ldisc_wait() smarter. That
+			 * is up for discussion.
+			 */
+			if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
+				return -ERESTARTSYS;
+			goto restart;
+		}
+		if(o_tty && o_tty->ldisc.refcount) {
+			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+			tty_ldisc_put(ldisc);
+			if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
+				return -ERESTARTSYS;
+			goto restart;
+		}
+	}
+
+	/* if the TTY_LDISC bit is set, then we are racing against another ldisc change */
+
+	if (!test_bit(TTY_LDISC, &tty->flags)) {
 		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
 		tty_ldisc_put(ldisc);
-		/*
-		 * There are several reasons we may be busy, including
-		 * random momentary I/O traffic. We must therefore
-		 * retry. We could distinguish between blocking ops
-		 * and retries if we made tty_ldisc_wait() smarter. That
-		 * is up for discussion.
-		 */
-		if(wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
-			return -ERESTARTSYS;			
+		ld = tty_ldisc_ref_wait(tty);
+		tty_ldisc_deref(ld);
 		goto restart;
 	}
-	clear_bit(TTY_LDISC, &tty->flags);	
-	clear_bit(TTY_DONT_FLIP, &tty->flags);
+
+	clear_bit(TTY_LDISC, &tty->flags);
+	if (o_tty)
+		clear_bit(TTY_LDISC, &o_tty->flags);
 	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
-	
+
 	/*
 	 *	From this point on we know nobody has an ldisc
 	 *	usage reference, nor can they obtain one until
 	 *	we say so later on.
 	 */
-	 
-	work = cancel_delayed_work(&tty->flip.work);
+
+	work = cancel_delayed_work(&tty->buf.work);
 	/*
-	 * Wait for ->hangup_work and ->flip.work handlers to terminate
+	 * Wait for ->hangup_work and ->buf.work handlers to terminate
 	 */
 	 
 	flush_scheduled_work();
@@ -569,17 +1058,27 @@
 	 */
 	 
 	tty_ldisc_enable(tty);
+	if (o_tty)
+		tty_ldisc_enable(o_tty);
 	
 	/* Restart it in case no characters kick it off. Safe if
 	   already running */
-	if(work)
-		schedule_delayed_work(&tty->flip.work, 1);
+	if (work)
+		schedule_delayed_work(&tty->buf.work, 1);
 	return retval;
 }
 
-/*
- * This routine returns a tty driver structure, given a device number
+/**
+ *	get_tty_driver		-	find device of a tty
+ *	@dev_t: device identifier
+ *	@index: returns the index of the tty
+ *
+ *	This routine returns a tty driver structure, given a device number
+ *	and also passes back the index number.
+ *
+ *	Locking: caller must hold tty_mutex
  */
+
 static struct tty_driver *get_tty_driver(dev_t device, int *index)
 {
 	struct tty_driver *p;
@@ -594,26 +1093,32 @@
 	return NULL;
 }
 
-/*
- * If we try to write to, or set the state of, a terminal and we're
- * not in the foreground, send a SIGTTOU.  If the signal is blocked or
- * ignored, go ahead and perform the operation.  (POSIX 7.2)
+/**
+ *	tty_check_change	-	check for POSIX terminal changes
+ *	@tty: tty to check
+ *
+ *	If we try to write to, or set the state of, a terminal and we're
+ *	not in the foreground, send a SIGTTOU.  If the signal is blocked or
+ *	ignored, go ahead and perform the operation.  (POSIX 7.2)
+ *
+ *	Locking: none
  */
+
 int tty_check_change(struct tty_struct * tty)
 {
 	if (current->signal->tty != tty)
 		return 0;
-	if (tty->pgrp <= 0) {
-		printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
+	if (!tty->pgrp) {
+		printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
 		return 0;
 	}
-	if (process_group(current) == tty->pgrp)
+	if (task_pgrp(current) == tty->pgrp)
 		return 0;
 	if (is_ignored(SIGTTOU))
 		return 0;
-	if (is_orphaned_pgrp(process_group(current)))
+	if (is_current_pgrp_orphaned())
 		return -EIO;
-	(void) kill_pg(process_group(current), SIGTTOU, 1);
+	(void) kill_pgrp(task_pgrp(current), SIGTTOU, 1);
 	return -ERESTARTSYS;
 }
 
@@ -643,7 +1148,7 @@
 	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
 }
 
-static struct file_operations tty_fops = {
+static const struct file_operations tty_fops = {
 	.llseek		= no_llseek,
 	.read		= tty_read,
 	.write		= tty_write,
@@ -655,7 +1160,7 @@
 };
 
 #ifdef CONFIG_UNIX98_PTYS
-static struct file_operations ptmx_fops = {
+static const struct file_operations ptmx_fops = {
 	.llseek		= no_llseek,
 	.read		= tty_read,
 	.write		= tty_write,
@@ -667,7 +1172,7 @@
 };
 #endif
 
-static struct file_operations console_fops = {
+static const struct file_operations console_fops = {
 	.llseek		= no_llseek,
 	.read		= tty_read,
 	.write		= redirected_tty_write,
@@ -678,7 +1183,7 @@
 	.fasync		= tty_fasync,
 };
 
-static struct file_operations hung_up_tty_fops = {
+static const struct file_operations hung_up_tty_fops = {
 	.llseek		= no_llseek,
 	.read		= hung_up_tty_read,
 	.write		= hung_up_tty_write,
@@ -735,15 +1240,49 @@
 }
 
 EXPORT_SYMBOL_GPL(tty_ldisc_flush);
+
+/**
+ *	tty_reset_termios	-	reset terminal state
+ *	@tty: tty to reset
+ *
+ *	Restore a terminal to the driver default state
+ */
+
+static void tty_reset_termios(struct tty_struct *tty)
+{
+	mutex_lock(&tty->termios_mutex);
+	*tty->termios = tty->driver->init_termios;
+	tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
+	tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
+	mutex_unlock(&tty->termios_mutex);
+}
 	
-/*
- * This can be called by the "eventd" kernel thread.  That is process synchronous,
- * but doesn't hold any locks, so we need to make sure we have the appropriate
- * locks for what we're doing..
+/**
+ *	do_tty_hangup		-	actual handler for hangup events
+ *	@work: tty device
+ *
+ *	This can be called by the "eventd" kernel thread.  That is process
+ *	synchronous but doesn't hold any locks, so we need to make sure we
+ *	have the appropriate locks for what we're doing.
+ *
+ *	The hangup event clears any pending redirections onto the hung up
+ *	device. It ensures future writes will error and it does the needed
+ *	line discipline hangup and signal delivery. The tty object itself
+ *	remains intact.
+ *
+ *	Locking:
+ *		BKL
+ *		  redirect lock for undoing redirection
+ *		  file list lock for manipulating list of ttys
+ *		  tty_ldisc_lock from called functions
+ *		  termios_mutex resetting termios data
+ *		  tasklist_lock to walk task list for hangup event
+ *		    ->siglock to protect ->signal/->sighand
  */
-static void do_tty_hangup(void *data)
+static void do_tty_hangup(struct work_struct *work)
 {
-	struct tty_struct *tty = (struct tty_struct *) data;
+	struct tty_struct *tty =
+		container_of(work, struct tty_struct, hangup_work);
 	struct file * cons_filp = NULL;
 	struct file *filp, *f = NULL;
 	struct task_struct *p;
@@ -766,7 +1305,7 @@
 	check_tty_count(tty, "do_tty_hangup");
 	file_list_lock();
 	/* This breaks for file handles being sent over AF_UNIX sockets ? */
-	list_for_each_entry(filp, &tty->tty_files, f_list) {
+	list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
 		if (filp->f_op->write == redirected_tty_write)
 			cons_filp = filp;
 		if (filp->f_op->write != tty_write)
@@ -805,11 +1344,7 @@
 	 * N_TTY.
 	 */
 	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
-	{
-		down(&tty->termios_sem);
-		*tty->termios = tty->driver->init_termios;
-		up(&tty->termios_sem);
-	}
+		tty_reset_termios(tty);
 	
 	/* Defer ldisc switch */
 	/* tty_deferred_ldisc_switch(N_TTY);
@@ -818,23 +1353,30 @@
 	  tty_release is called */
 	
 	read_lock(&tasklist_lock);
-	if (tty->session > 0) {
-		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
+	if (tty->session) {
+		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
+			spin_lock_irq(&p->sighand->siglock);
 			if (p->signal->tty == tty)
 				p->signal->tty = NULL;
-			if (!p->signal->leader)
+			if (!p->signal->leader) {
+				spin_unlock_irq(&p->sighand->siglock);
 				continue;
-			send_group_sig_info(SIGHUP, SEND_SIG_PRIV, p);
-			send_group_sig_info(SIGCONT, SEND_SIG_PRIV, p);
-			if (tty->pgrp > 0)
-				p->signal->tty_old_pgrp = tty->pgrp;
-		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
+			}
+			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
+			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
+			put_pid(p->signal->tty_old_pgrp);  /* A noop */
+			if (tty->pgrp)
+				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
+			spin_unlock_irq(&p->sighand->siglock);
+		} while_each_pid_task(tty->session, PIDTYPE_SID, p);
 	}
 	read_unlock(&tasklist_lock);
 
 	tty->flags = 0;
-	tty->session = 0;
-	tty->pgrp = -1;
+	put_pid(tty->session);
+	put_pid(tty->pgrp);
+	tty->session = NULL;
+	tty->pgrp = NULL;
 	tty->ctrl_status = 0;
 	/*
 	 *	If one of the devices matches a console pointer, we
@@ -864,6 +1406,14 @@
 		fput(f);
 }
 
+/**
+ *	tty_hangup		-	trigger a hangup event
+ *	@tty: tty to hangup
+ *
+ *	A carrier loss (virtual or otherwise) has occurred on this like
+ *	schedule a hangup sequence to run after this event.
+ */
+
 void tty_hangup(struct tty_struct * tty)
 {
 #ifdef TTY_DEBUG_HANGUP
@@ -876,6 +1426,15 @@
 
 EXPORT_SYMBOL(tty_hangup);
 
+/**
+ *	tty_vhangup		-	process vhangup
+ *	@tty: tty to hangup
+ *
+ *	The user has asked via system call for the terminal to be hung up.
+ *	We do this synchronously so that when the syscall returns the process
+ *	is complete. That guarantee is neccessary for security reasons.
+ */
+
 void tty_vhangup(struct tty_struct * tty)
 {
 #ifdef TTY_DEBUG_HANGUP
@@ -883,10 +1442,18 @@
 
 	printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
 #endif
-	do_tty_hangup((void *) tty);
+	do_tty_hangup(&tty->hangup_work);
 }
 EXPORT_SYMBOL(tty_vhangup);
 
+/**
+ *	tty_hung_up_p		-	was tty hung up
+ *	@filp: file pointer of tty
+ *
+ *	Return true if the tty has been subject to a vhangup or a carrier
+ *	loss
+ */
+
 int tty_hung_up_p(struct file * filp)
 {
 	return (filp->f_op == &hung_up_tty_fops);
@@ -894,65 +1461,123 @@
 
 EXPORT_SYMBOL(tty_hung_up_p);
 
-/*
- * This function is typically called only by the session leader, when
- * it wants to disassociate itself from its controlling tty.
+static void session_clear_tty(struct pid *session)
+{
+	struct task_struct *p;
+	do_each_pid_task(session, PIDTYPE_SID, p) {
+		proc_clear_tty(p);
+	} while_each_pid_task(session, PIDTYPE_SID, p);
+}
+
+/**
+ *	disassociate_ctty	-	disconnect controlling tty
+ *	@on_exit: true if exiting so need to "hang up" the session
  *
- * It performs the following functions:
+ *	This function is typically called only by the session leader, when
+ *	it wants to disassociate itself from its controlling tty.
+ *
+ *	It performs the following functions:
  * 	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
  * 	(2)  Clears the tty from being controlling the session
  * 	(3)  Clears the controlling tty for all processes in the
  * 		session group.
  *
- * The argument on_exit is set to 1 if called when a process is
- * exiting; it is 0 if called by the ioctl TIOCNOTTY.
+ *	The argument on_exit is set to 1 if called when a process is
+ *	exiting; it is 0 if called by the ioctl TIOCNOTTY.
+ *
+ *	Locking:
+ *		BKL is taken for hysterical raisins
+ *		  tty_mutex is taken to protect tty
+ *		  ->siglock is taken to protect ->signal/->sighand
+ *		  tasklist_lock is taken to walk process list for sessions
+ *		    ->siglock is taken to protect ->signal/->sighand
  */
+
 void disassociate_ctty(int on_exit)
 {
 	struct tty_struct *tty;
-	struct task_struct *p;
-	int tty_pgrp = -1;
+	struct pid *tty_pgrp = NULL;
 
 	lock_kernel();
 
-	down(&tty_sem);
-	tty = current->signal->tty;
+	mutex_lock(&tty_mutex);
+	tty = get_current_tty();
 	if (tty) {
-		tty_pgrp = tty->pgrp;
-		up(&tty_sem);
+		tty_pgrp = get_pid(tty->pgrp);
+		mutex_unlock(&tty_mutex);
+		/* XXX: here we race, there is nothing protecting tty */
 		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
 			tty_vhangup(tty);
-	} else {
-		if (current->signal->tty_old_pgrp) {
-			kill_pg(current->signal->tty_old_pgrp, SIGHUP, on_exit);
-			kill_pg(current->signal->tty_old_pgrp, SIGCONT, on_exit);
+	} else if (on_exit) {
+		struct pid *old_pgrp;
+		spin_lock_irq(&current->sighand->siglock);
+		old_pgrp = current->signal->tty_old_pgrp;
+		current->signal->tty_old_pgrp = NULL;
+		spin_unlock_irq(&current->sighand->siglock);
+		if (old_pgrp) {
+			kill_pgrp(old_pgrp, SIGHUP, on_exit);
+			kill_pgrp(old_pgrp, SIGCONT, on_exit);
+			put_pid(old_pgrp);
 		}
-		up(&tty_sem);
+		mutex_unlock(&tty_mutex);
 		unlock_kernel();	
 		return;
 	}
-	if (tty_pgrp > 0) {
-		kill_pg(tty_pgrp, SIGHUP, on_exit);
+	if (tty_pgrp) {
+		kill_pgrp(tty_pgrp, SIGHUP, on_exit);
 		if (!on_exit)
-			kill_pg(tty_pgrp, SIGCONT, on_exit);
+			kill_pgrp(tty_pgrp, SIGCONT, on_exit);
+		put_pid(tty_pgrp);
 	}
 
-	/* Must lock changes to tty_old_pgrp */
-	down(&tty_sem);
-	current->signal->tty_old_pgrp = 0;
-	tty->session = 0;
-	tty->pgrp = -1;
+	spin_lock_irq(&current->sighand->siglock);
+	tty_pgrp = current->signal->tty_old_pgrp;
+	current->signal->tty_old_pgrp = NULL;
+	spin_unlock_irq(&current->sighand->siglock);
+	put_pid(tty_pgrp);
 
+	mutex_lock(&tty_mutex);
+	/* It is possible that do_tty_hangup has free'd this tty */
+	tty = get_current_tty();
+	if (tty) {
+		put_pid(tty->session);
+		put_pid(tty->pgrp);
+		tty->session = NULL;
+		tty->pgrp = NULL;
+	} else {
+#ifdef TTY_DEBUG_HANGUP
+		printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
+		       " = NULL", tty);
+#endif
+	}
+	mutex_unlock(&tty_mutex);
+
 	/* Now clear signal->tty under the lock */
 	read_lock(&tasklist_lock);
-	do_each_task_pid(current->signal->session, PIDTYPE_SID, p) {
-		p->signal->tty = NULL;
-	} while_each_task_pid(current->signal->session, PIDTYPE_SID, p);
+	session_clear_tty(task_session(current));
 	read_unlock(&tasklist_lock);
-	up(&tty_sem);
 	unlock_kernel();
 }
 
+
+/**
+ *	stop_tty	-	propogate flow control
+ *	@tty: tty to stop
+ *
+ *	Perform flow control to the driver. For PTY/TTY pairs we
+ *	must also propogate the TIOCKPKT status. May be called
+ *	on an already stopped device and will not re-call the driver
+ *	method.
+ *
+ *	This functionality is used by both the line disciplines for
+ *	halting incoming flow and by the driver. It may therefore be
+ *	called from any context, may be under the tty atomic_write_lock
+ *	but not always.
+ *
+ *	Locking:
+ *		Broken. Relies on BKL which is unsafe here.
+ */
+
 void stop_tty(struct tty_struct *tty)
 {
 	if (tty->stopped)
@@ -969,6 +1594,19 @@
 
 EXPORT_SYMBOL(stop_tty);
 
+/**
+ *	start_tty	-	propogate flow control
+ *	@tty: tty to start
+ *
+ *	Start a tty that has been stopped if at all possible. Perform
+ *	any neccessary wakeups and propogate the TIOCPKT status. If this
+ *	is the tty was previous stopped and is being started then the
+ *	driver start method is invoked and the line discipline woken.
+ *
+ *	Locking:
+ *		Broken. Relies on BKL which is unsafe here.
+ */
+
 void start_tty(struct tty_struct *tty)
 {
 	if (!tty->stopped || tty->flow_stopped)
@@ -984,11 +1622,27 @@
 
 	/* If we have a running line discipline it may need kicking */
 	tty_wakeup(tty);
-	wake_up_interruptible(&tty->write_wait);
 }
 
 EXPORT_SYMBOL(start_tty);
 
+/**
+ *	tty_read	-	read method for tty device files
+ *	@file: pointer to tty file
+ *	@buf: user buffer
+ *	@count: size of user buffer
+ *	@ppos: unused
+ *
+ *	Perform the read system call function on this terminal device. Checks
+ *	for hung up devices before calling the line discipline method.
+ *
+ *	Locking:
+ *		Locks the line discipline internally while needed
+ *		For historical reasons the line discipline read method is
+ *	invoked under the BKL. This will go away in time so do not rely on it
+ *	in new code. Multiple read calls may be outstanding in parallel.
+ */
+
 static ssize_t tty_read(struct file * file, char __user * buf, size_t count, 
 			loff_t *ppos)
 {
@@ -998,7 +1652,7 @@
 	struct tty_ldisc *ld;
 
 	tty = (struct tty_struct *)file->private_data;
-	inode = file->f_dentry->d_inode;
+	inode = file->f_path.dentry->d_inode;
 	if (tty_paranoia_check(tty, inode, "tty_read"))
 		return -EIO;
 	if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
@@ -1033,7 +1687,8 @@
 	ssize_t ret = 0, written = 0;
 	unsigned int chunk;
 	
-	if (down_interruptible(&tty->atomic_write)) {
+	/* FIXME: O_NDELAY ... */
+	if (mutex_lock_interruptible(&tty->atomic_write_lock)) {
 		return -ERESTARTSYS;
 	}
 
@@ -1049,6 +1704,9 @@
 	 * layer has problems with bigger chunks. It will
 	 * claim to be able to handle more characters than
 	 * it actually does.
+	 *
+	 * FIXME: This can probably go away now except that 64K chunks
+	 * are too likely to fail unless switched to vmalloc...
 	 */
 	chunk = 2048;
 	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
@@ -1056,7 +1714,7 @@
 	if (count < chunk)
 		chunk = count;
 
-	/* write_buf/write_cnt is protected by the atomic_write semaphore */
+	/* write_buf/write_cnt is protected by the atomic_write_lock mutex */
 	if (tty->write_cnt < chunk) {
 		unsigned char *buf;
 
@@ -1065,7 +1723,7 @@
 
 		buf = kmalloc(chunk, GFP_KERNEL);
 		if (!buf) {
-			up(&tty->atomic_write);
+			mutex_unlock(&tty->atomic_write_lock);
 			return -ENOMEM;
 		}
 		kfree(tty->write_buf);
@@ -1097,20 +1755,38 @@
 		cond_resched();
 	}
 	if (written) {
-		struct inode *inode = file->f_dentry->d_inode;
+		struct inode *inode = file->f_path.dentry->d_inode;
 		inode->i_mtime = current_fs_time(inode->i_sb);
 		ret = written;
 	}
-	up(&tty->atomic_write);
+	mutex_unlock(&tty->atomic_write_lock);
 	return ret;
 }
 
 
+/**
+ *	tty_write		-	write method for tty device file
+ *	@file: tty file pointer
+ *	@buf: user data to write
+ *	@count: bytes to write
+ *	@ppos: unused
+ *
+ *	Write data to a tty device via the line discipline.
+ *
+ *	Locking:
+ *		Locks the line discipline as required
+ *		Writes to the tty driver are serialized by the atomic_write_lock
+ *	and are then processed in chunks to the device. The line discipline
+ *	write method will not be involked in parallel for each device
+ *		The line discipline write method is called under the big
+ *	kernel lock for historical reasons. New code should not rely on this.
+ */
+
 static ssize_t tty_write(struct file * file, const char __user * buf, size_t count,
 			 loff_t *ppos)
 {
 	struct tty_struct * tty;
-	struct inode *inode = file->f_dentry->d_inode;
+	struct inode *inode = file->f_path.dentry->d_inode;
 	ssize_t ret;
 	struct tty_ldisc *ld;
 	
@@ -1153,7 +1829,18 @@
 
 static char ptychar[] = "pqrstuvwxyzabcde";
 
-static inline void pty_line_name(struct tty_driver *driver, int index, char *p)
+/**
+ *	pty_line_name	-	generate name for a pty
+ *	@driver: the tty driver in use
+ *	@index: the minor number
+ *	@p: output buffer of at least 6 bytes
+ *
+ *	Generate a name from a driver reference and write it to the output
+ *	buffer.
+ *
+ *	Locking: None
+ */
+static void pty_line_name(struct tty_driver *driver, int index, char *p)
 {
 	int i = index + driver->name_base;
 	/* ->name is initialized to "ttyp", but "tty" is expected */
@@ -1162,28 +1849,71 @@
 			ptychar[i >> 4 & 0xf], i & 0xf);
 }
 
-static inline void tty_line_name(struct tty_driver *driver, int index, char *p)
+/**
+ *	pty_line_name	-	generate name for a tty
+ *	@driver: the tty driver in use
+ *	@index: the minor number
+ *	@p: output buffer of at least 7 bytes
+ *
+ *	Generate a name from a driver reference and write it to the output
+ *	buffer.
+ *
+ *	Locking: None
+ */
+static void tty_line_name(struct tty_driver *driver, int index, char *p)
 {
 	sprintf(p, "%s%d", driver->name, index + driver->name_base);
 }
 
-/*
+/**
+ *	init_dev		-	initialise a tty device
+ *	@driver: tty driver we are opening a device on
+ *	@idx: device index
+ *	@tty: returned tty structure
+ *
+ *	Prepare a tty device. This may not be a "new" clean device but
+ *	could also be an active device. The pty drivers require special
+ *	handling because of this.
+ *
+ *	Locking:
+ *		The function is called under the tty_mutex, which
+ *	protects us from the tty struct or driver itself going away.
+ *
+ *	On exit the tty device has the line discipline attached and
+ *	a reference count of 1. If a pair was created for pty/tty use
+ *	and the other was a pty master then it too has a reference count of 1.
+ *
  * WSH 06/09/97: Rewritten to remove races and properly clean up after a
- * failed open.  The new code protects the open with a semaphore, so it's
- * really quite straightforward.  The semaphore locking can probably be
+ * failed open.  The new code protects the open with a mutex, so it's
+ * really quite straightforward.  The mutex locking can probably be
  * relaxed for the (most common) case of reopening a tty.
  */
+
 static int init_dev(struct tty_driver *driver, int idx,
 	struct tty_struct **ret_tty)
 {
 	struct tty_struct *tty, *o_tty;
-	struct termios *tp, **tp_loc, *o_tp, **o_tp_loc;
-	struct termios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
-	int retval=0;
+	struct ktermios *tp, **tp_loc, *o_tp, **o_tp_loc;
+	struct ktermios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
+	int retval = 0;
 
 	/* check whether we're reopening an existing tty */
 	if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
 		tty = devpts_get_tty(idx);
+		/*
+		 * If we don't have a tty here on a slave open, it's because
+		 * the master already started the close process and there's
+		 * no relation between devpts file and tty anymore.
+		 */
+		if (!tty && driver->subtype == PTY_TYPE_SLAVE) {
+			retval = -EIO;
+			goto end_init;
+		}
+		/*
+		 * It's safe from now on because init_dev() is called with
+		 * tty_mutex held and release_dev() won't change tty->count
+		 * or tty->flags without having to grab tty_mutex
+		 */
 		if (tty && driver->subtype == PTY_TYPE_MASTER)
 			tty = tty->link;
 	} else {
@@ -1225,7 +1955,7 @@
 	}
 
 	if (!*tp_loc) {
-		tp = (struct termios *) kmalloc(sizeof(struct termios),
+		tp = (struct ktermios *) kmalloc(sizeof(struct ktermios),
 						GFP_KERNEL);
 		if (!tp)
 			goto free_mem_out;
@@ -1233,11 +1963,11 @@
 	}
 
 	if (!*ltp_loc) {
-		ltp = (struct termios *) kmalloc(sizeof(struct termios),
+		ltp = (struct ktermios *) kmalloc(sizeof(struct ktermios),
 						 GFP_KERNEL);
 		if (!ltp)
 			goto free_mem_out;
-		memset(ltp, 0, sizeof(struct termios));
+		memset(ltp, 0, sizeof(struct ktermios));
 	}
 
 	if (driver->type == TTY_DRIVER_TYPE_PTY) {
@@ -1258,19 +1988,19 @@
 		}
 
 		if (!*o_tp_loc) {
-			o_tp = (struct termios *)
-				kmalloc(sizeof(struct termios), GFP_KERNEL);
+			o_tp = (struct ktermios *)
+				kmalloc(sizeof(struct ktermios), GFP_KERNEL);
 			if (!o_tp)
 				goto free_mem_out;
 			*o_tp = driver->other->init_termios;
 		}
 
 		if (!*o_ltp_loc) {
-			o_ltp = (struct termios *)
-				kmalloc(sizeof(struct termios), GFP_KERNEL);
+			o_ltp = (struct ktermios *)
+				kmalloc(sizeof(struct ktermios), GFP_KERNEL);
 			if (!o_ltp)
 				goto free_mem_out;
-			memset(o_ltp, 0, sizeof(struct termios));
+			memset(o_ltp, 0, sizeof(struct ktermios));
 		}
 
 		/*
@@ -1296,7 +2026,7 @@
 
 	/* 
 	 * All structures have been allocated, so now we install them.
-	 * Failures after this point use release_mem to clean up, so 
+	 * Failures after this point use release_tty to clean up, so
 	 * there's no need to null out the local pointers.
 	 */
 	if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
@@ -1309,13 +2039,16 @@
 		*ltp_loc = ltp;
 	tty->termios = *tp_loc;
 	tty->termios_locked = *ltp_loc;
+	/* Compatibility until drivers always set this */
+	tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
+	tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
 	driver->refcount++;
 	tty->count++;
 
 	/* 
 	 * Structures all installed ... call the ldisc open routines.
-	 * If we fail here just call release_mem to clean up.  No need
-	 * to decrement the use counts, as release_mem doesn't care.
+	 * If we fail here just call release_tty to clean up.  No need
+	 * to decrement the use counts, as release_tty doesn't care.
 	 */
 
 	if (tty->ldisc.open) {
@@ -1367,20 +2100,17 @@
 success:
 	*ret_tty = tty;
 	
-	/* All paths come through here to release the semaphore */
+	/* All paths come through here to release the mutex */
 end_init:
 	return retval;
 
 	/* Release locally allocated memory ... nothing placed in slots */
 free_mem_out:
-	if (o_tp)
-		kfree(o_tp);
+	kfree(o_tp);
 	if (o_tty)
 		free_tty_struct(o_tty);
-	if (ltp)
-		kfree(ltp);
-	if (tp)
-		kfree(tp);
+	kfree(ltp);
+	kfree(tp);
 	free_tty_struct(tty);
 
 fail_no_mem:
@@ -1388,48 +2118,36 @@
 	retval = -ENOMEM;
 	goto end_init;
 
-	/* call the tty release_mem routine to clean out this slot */
+	/* call the tty release_tty routine to clean out this slot */
 release_mem_out:
-	printk(KERN_INFO "init_dev: ldisc open failed, "
-			 "clearing slot %d\n", idx);
-	release_mem(tty, idx);
+	if (printk_ratelimit())
+		printk(KERN_INFO "init_dev: ldisc open failed, "
+				 "clearing slot %d\n", idx);
+	release_tty(tty, idx);
 	goto end_init;
 }
 
-/*
- * Releases memory associated with a tty structure, and clears out the
- * driver table slots.
+/**
+ *	release_one_tty		-	release tty structure memory
+ *
+ *	Releases memory associated with a tty structure, and clears out the
+ *	driver table slots. This function is called when a device is no longer
+ *	in use. It also gets called when setup of a device fails.
+ *
+ *	Locking:
+ *		tty_mutex - sometimes only
+ *		takes the file list lock internally when working on the list
+ *	of ttys that the driver keeps.
+ *		FIXME: should we require tty_mutex is held here ??
  */
-static void release_mem(struct tty_struct *tty, int idx)
+static void release_one_tty(struct tty_struct *tty, int idx)
 {
-	struct tty_struct *o_tty;
-	struct termios *tp;
 	int devpts = tty->driver->flags & TTY_DRIVER_DEVPTS_MEM;
+	struct ktermios *tp;
 
-	if ((o_tty = tty->link) != NULL) {
-		if (!devpts)
-			o_tty->driver->ttys[idx] = NULL;
-		if (o_tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
-			tp = o_tty->termios;
-			if (!devpts)
-				o_tty->driver->termios[idx] = NULL;
-			kfree(tp);
-
-			tp = o_tty->termios_locked;
-			if (!devpts)
-				o_tty->driver->termios_locked[idx] = NULL;
-			kfree(tp);
-		}
-		o_tty->magic = 0;
-		o_tty->driver->refcount--;
-		file_list_lock();
-		list_del_init(&o_tty->tty_files);
-		file_list_unlock();
-		free_tty_struct(o_tty);
-	}
-
 	if (!devpts)
 		tty->driver->ttys[idx] = NULL;
+
 	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
 		tp = tty->termios;
 		if (!devpts)
@@ -1442,15 +2160,39 @@
 		kfree(tp);
 	}
 
+
 	tty->magic = 0;
 	tty->driver->refcount--;
+
 	file_list_lock();
 	list_del_init(&tty->tty_files);
 	file_list_unlock();
-	module_put(tty->driver->owner);
+
 	free_tty_struct(tty);
 }
 
+/**
+ *	release_tty		-	release tty structure memory
+ *
+ *	Release both @tty and a possible linked partner (think pty pair),
+ *	and decrement the refcount of the backing module.
+ *
+ *	Locking:
+ *		tty_mutex - sometimes only
+ *		takes the file list lock internally when working on the list
+ *	of ttys that the driver keeps.
+ *		FIXME: should we require tty_mutex is held here ??
+ */
+static void release_tty(struct tty_struct *tty, int idx)
+{
+	struct tty_driver *driver = tty->driver;
+
+	if (tty->link)
+		release_one_tty(tty->link, idx);
+	release_one_tty(tty, idx);
+	module_put(driver->owner);
+}
+
 /*
  * Even releasing the tty structures is a tricky business.. We have
  * to be very careful that the structures are all released at the
@@ -1463,13 +2205,13 @@
 {
 	struct tty_struct *tty, *o_tty;
 	int	pty_master, tty_closing, o_tty_closing, do_sleep;
-	int	devpts_master, devpts;
+	int	devpts;
 	int	idx;
 	char	buf[64];
 	unsigned long flags;
 	
 	tty = (struct tty_struct *)filp->private_data;
-	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "release_dev"))
+	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "release_dev"))
 		return;
 
 	check_tty_count(tty, "release_dev");
@@ -1480,7 +2222,6 @@
 	pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
 		      tty->driver->subtype == PTY_TYPE_MASTER);
 	devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
-	devpts_master = pty_master && devpts;
 	o_tty = tty->link;
 
 #ifdef TTY_PARANOIA_CHECK
@@ -1567,11 +2308,10 @@
 		/* Guard against races with tty->count changes elsewhere and
 		   opens on /dev/tty */
 		   
-		down(&tty_sem);
+		mutex_lock(&tty_mutex);
 		tty_closing = tty->count <= 1;
 		o_tty_closing = o_tty &&
 			(o_tty->count <= (pty_master ? 1 : 0));
-		up(&tty_sem);
 		do_sleep = 0;
 
 		if (tty_closing) {
@@ -1599,6 +2339,7 @@
 
 		printk(KERN_WARNING "release_dev: %s: read/write wait queue "
 				    "active!\n", tty_name(tty, buf));
+		mutex_unlock(&tty_mutex);
 		schedule();
 	}	
 
@@ -1607,8 +2348,6 @@
 	 * both sides, and we've completed the last operation that could 
 	 * block, so it's safe to proceed with closing.
 	 */
-	 
-	down(&tty_sem);
 	if (pty_master) {
 		if (--o_tty->count < 0) {
 			printk(KERN_WARNING "release_dev: bad pty slave count "
@@ -1622,7 +2361,6 @@
 		       tty->count, tty_name(tty, buf));
 		tty->count = 0;
 	}
-	up(&tty_sem);
 	
 	/*
 	 * We've decremented tty->count, so we need to remove this file
@@ -1654,19 +2392,15 @@
 	 * tty.
 	 */
 	if (tty_closing || o_tty_closing) {
-		struct task_struct *p;
-
 		read_lock(&tasklist_lock);
-		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
-			p->signal->tty = NULL;
-		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
+		session_clear_tty(tty->session);
 		if (o_tty)
-			do_each_task_pid(o_tty->session, PIDTYPE_SID, p) {
-				p->signal->tty = NULL;
-			} while_each_task_pid(o_tty->session, PIDTYPE_SID, p);
+			session_clear_tty(o_tty->session);
 		read_unlock(&tasklist_lock);
 	}
 
+	mutex_unlock(&tty_mutex);
+
 	/* check whether both sides are closing ... */
 	if (!tty_closing || (o_tty && !o_tty_closing))
 		return;
@@ -1680,11 +2414,10 @@
 	 * race with the set_ldisc code path.
 	 */
 	clear_bit(TTY_LDISC, &tty->flags);
-	clear_bit(TTY_DONT_FLIP, &tty->flags);
-	cancel_delayed_work(&tty->flip.work);
+	cancel_delayed_work(&tty->buf.work);
 
 	/*
-	 * Wait for ->hangup_work and ->flip.work handlers to terminate
+	 * Wait for ->hangup_work and ->buf.work handlers to terminate
 	 */
 	 
 	flush_scheduled_work();
@@ -1727,10 +2460,10 @@
 		tty_set_termios_ldisc(o_tty,N_TTY); 
 	}
 	/*
-	 * The release_mem function takes care of the details of clearing
+	 * The release_tty function takes care of the details of clearing
 	 * the slots and preserving the termios structure.
 	 */
-	release_mem(tty, idx);
+	release_tty(tty, idx);
 
 #ifdef CONFIG_UNIX98_PTYS
 	/* Make this pty number available for reallocation */
@@ -1743,18 +2476,27 @@
 
 }
 
-/*
- * tty_open and tty_release keep up the tty count that contains the
- * number of opens done on a tty. We cannot use the inode-count, as
- * different inodes might point to the same tty.
+/**
+ *	tty_open		-	open a tty device
+ *	@inode: inode of device file
+ *	@filp: file pointer to tty
  *
- * Open-counting is needed for pty masters, as well as for keeping
- * track of serial lines: DTR is dropped when the last close happens.
- * (This is not done solely through tty->count, now.  - Ted 1/27/92)
+ *	tty_open and tty_release keep up the tty count that contains the
+ *	number of opens done on a tty. We cannot use the inode-count, as
+ *	different inodes might point to the same tty.
  *
- * The termios state of a pty is reset on first open so that
- * settings don't persist across reuse.
+ *	Open-counting is needed for pty masters, as well as for keeping
+ *	track of serial lines: DTR is dropped when the last close happens.
+ *	(This is not done solely through tty->count, now.  - Ted 1/27/92)
+ *
+ *	The termios state of a pty is reset on first open so that
+ *	settings don't persist across reuse.
+ *
+ *	Locking: tty_mutex protects tty, get_tty_driver and init_dev work.
+ *		 tty->count should protect the rest.
+ *		 ->siglock protects ->signal/->sighand
  */
+
 static int tty_open(struct inode * inode, struct file * filp)
 {
 	struct tty_struct *tty;
@@ -1763,6 +2505,7 @@
 	int index;
 	dev_t device = inode->i_rdev;
 	unsigned short saved_flags = filp->f_flags;
+	struct pid *old_pgrp;
 
 	nonseekable_open(inode, filp);
 	
@@ -1771,15 +2514,16 @@
 	index  = -1;
 	retval = 0;
 	
-	down(&tty_sem);
+	mutex_lock(&tty_mutex);
 
 	if (device == MKDEV(TTYAUX_MAJOR,0)) {
-		if (!current->signal->tty) {
-			up(&tty_sem);
+		tty = get_current_tty();
+		if (!tty) {
+			mutex_unlock(&tty_mutex);
 			return -ENXIO;
 		}
-		driver = current->signal->tty->driver;
-		index = current->signal->tty->index;
+		driver = tty->driver;
+		index = tty->index;
 		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
 		/* noctty = 1; */
 		goto got_driver;
@@ -1811,18 +2555,18 @@
 			noctty = 1;
 			goto got_driver;
 		}
-		up(&tty_sem);
+		mutex_unlock(&tty_mutex);
 		return -ENODEV;
 	}
 
 	driver = get_tty_driver(device, &index);
 	if (!driver) {
-		up(&tty_sem);
+		mutex_unlock(&tty_mutex);
 		return -ENODEV;
 	}
 got_driver:
 	retval = init_dev(driver, index, &tty);
-	up(&tty_sem);
+	mutex_unlock(&tty_mutex);
 	if (retval)
 		return retval;
 
@@ -1864,21 +2608,34 @@
 			filp->f_op = &tty_fops;
 		goto retry_open;
 	}
+
+	old_pgrp = NULL;
+	mutex_lock(&tty_mutex);
+	spin_lock_irq(&current->sighand->siglock);
 	if (!noctty &&
 	    current->signal->leader &&
 	    !current->signal->tty &&
-	    tty->session == 0) {
-	    	task_lock(current);
-		current->signal->tty = tty;
-		task_unlock(current);
-		current->signal->tty_old_pgrp = 0;
-		tty->session = current->signal->session;
-		tty->pgrp = process_group(current);
-	}
+	    tty->session == NULL)
+		old_pgrp = __proc_set_tty(current, tty);
+	spin_unlock_irq(&current->sighand->siglock);
+	mutex_unlock(&tty_mutex);
+	put_pid(old_pgrp);
 	return 0;
 }
 
 #ifdef CONFIG_UNIX98_PTYS
+/**
+ *	ptmx_open		-	open a unix 98 pty master
+ *	@inode: inode of device file
+ *	@filp: file pointer to tty
+ *
+ *	Allocate a unix98 pty master device from the ptmx driver.
+ *
+ *	Locking: tty_mutex protects theinit_dev work. tty->count should
+ 		protect the rest.
+ *		allocated_ptys_lock handles the list of free pty numbers
+ */
+
 static int ptmx_open(struct inode * inode, struct file * filp)
 {
 	struct tty_struct *tty;
@@ -1908,9 +2665,9 @@
 	}
 	up(&allocated_ptys_lock);
 
-	down(&tty_sem);
+	mutex_lock(&tty_mutex);
 	retval = init_dev(ptm_driver, index, &tty);
-	up(&tty_sem);
+	mutex_unlock(&tty_mutex);
 	
 	if (retval)
 		goto out;
@@ -1929,6 +2686,7 @@
 		return 0;
 out1:
 	release_dev(filp);
+	return retval;
 out:
 	down(&allocated_ptys_lock);
 	idr_remove(&allocated_ptys, index);
@@ -1937,6 +2695,18 @@
 }
 #endif
 
+/**
+ *	tty_release		-	vfs callback for close
+ *	@inode: inode of tty
+ *	@filp: file pointer for handle to tty
+ *
+ *	Called the last time each file handle is closed that references
+ *	this tty. There may however be several such references.
+ *
+ *	Locking:
+ *		Takes bkl. See release_dev
+ */
+
 static int tty_release(struct inode * inode, struct file * filp)
 {
 	lock_kernel();
@@ -1945,7 +2715,18 @@
 	return 0;
 }
 
-/* No kernel lock held - fine */
+/**
+ *	tty_poll	-	check tty status
+ *	@filp: file being polled
+ *	@wait: poll wait structures to update
+ *
+ *	Call the line discipline polling method to obtain the poll
+ *	status of the device.
+ *
+ *	Locking: locks called line discipline but ldisc poll method
+ *	may be re-entered freely by other callers.
+ */
+
 static unsigned int tty_poll(struct file * filp, poll_table * wait)
 {
 	struct tty_struct * tty;
@@ -1953,7 +2734,7 @@
 	int ret = 0;
 
 	tty = (struct tty_struct *)filp->private_data;
-	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "tty_poll"))
+	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_poll"))
 		return 0;
 		
 	ld = tty_ldisc_ref_wait(tty);
@@ -1969,7 +2750,7 @@
 	int retval;
 
 	tty = (struct tty_struct *)filp->private_data;
-	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "tty_fasync"))
+	if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
 		return 0;
 	
 	retval = fasync_helper(fd, filp, on, &tty->fasync);
@@ -1977,9 +2758,18 @@
 		return retval;
 
 	if (on) {
+		enum pid_type type;
+		struct pid *pid;
 		if (!waitqueue_active(&tty->read_wait))
 			tty->minimum_to_wake = 1;
-		retval = f_setown(filp, (-tty->pgrp) ? : current->pid, 0);
+		if (tty->pgrp) {
+			pid = tty->pgrp;
+			type = PIDTYPE_PGID;
+		} else {
+			pid = task_pid(current);
+			type = PIDTYPE_PID;
+		}
+		retval = __f_setown(filp, pid, type, 0);
 		if (retval)
 			return retval;
 	} else {
@@ -1989,6 +2779,23 @@
 	return 0;
 }
 
+/**
+ *	tiocsti			-	fake input character
+ *	@tty: tty to fake input into
+ *	@p: pointer to character
+ *
+ *	Fake input to a tty device. Does the neccessary locking and
+ *	input management.
+ *
+ *	FIXME: does not honour flow control ??
+ *
+ *	Locking:
+ *		Called functions take tty_ldisc_lock
+ *		current->signal->tty check is safe without locks
+ *
+ *	FIXME: may race normal receive processing
+ */
+
 static int tiocsti(struct tty_struct *tty, char __user *p)
 {
 	char ch, mbz = 0;
@@ -2004,13 +2811,45 @@
 	return 0;
 }
 
+/**
+ *	tiocgwinsz		-	implement window query ioctl
+ *	@tty; tty
+ *	@arg: user buffer for result
+ *
+ *	Copies the kernel idea of the window size into the user buffer.
+ *
+ *	Locking: tty->termios_mutex is taken to ensure the winsize data
+ *		is consistent.
+ */
+
 static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
 {
-	if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
-		return -EFAULT;
-	return 0;
+	int err;
+
+	mutex_lock(&tty->termios_mutex);
+	err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
+	mutex_unlock(&tty->termios_mutex);
+
+	return err ? -EFAULT: 0;
 }
 
+/**
+ *	tiocswinsz		-	implement window size set ioctl
+ *	@tty; tty
+ *	@arg: user buffer for result
+ *
+ *	Copies the user idea of the window size to the kernel. Traditionally
+ *	this is just advisory information but for the Linux console it
+ *	actually has driver level meaning and triggers a VC resize.
+ *
+ *	Locking:
+ *		Called function use the console_sem is used to ensure we do
+ *	not try and resize the console twice at once.
+ *		The tty->termios_mutex is used to ensure we don't double
+ *	resize and get confused. Lock order - tty->termios_mutex before
+ *	console sem
+ */
+
 static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
 	struct winsize __user * arg)
 {
@@ -2018,28 +2857,40 @@
 
 	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
 		return -EFAULT;
+
+	mutex_lock(&tty->termios_mutex);
 	if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
-		return 0;
+		goto done;
+
 #ifdef CONFIG_VT
 	if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
-		int rc;
-
-		acquire_console_sem();
-		rc = vc_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row);
-		release_console_sem();
-		if (rc)
-			return -ENXIO;
+		if (vc_lock_resize(tty->driver_data, tmp_ws.ws_col,
+					tmp_ws.ws_row)) {
+			mutex_unlock(&tty->termios_mutex);
+ 			return -ENXIO;
+		}
 	}
 #endif
-	if (tty->pgrp > 0)
-		kill_pg(tty->pgrp, SIGWINCH, 1);
-	if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
-		kill_pg(real_tty->pgrp, SIGWINCH, 1);
+	if (tty->pgrp)
+		kill_pgrp(tty->pgrp, SIGWINCH, 1);
+	if ((real_tty->pgrp != tty->pgrp) && real_tty->pgrp)
+		kill_pgrp(real_tty->pgrp, SIGWINCH, 1);
 	tty->winsize = tmp_ws;
 	real_tty->winsize = tmp_ws;
+done:
+	mutex_unlock(&tty->termios_mutex);
 	return 0;
 }
 
+/**
+ *	tioccons	-	allow admin to move logical console
+ *	@file: the file to become console
+ *
+ *	Allow the adminstrator to move the redirected console device
+ *
+ *	Locking: uses redirect_lock to guard the redirect information
+ */
+
 static int tioccons(struct file *file)
 {
 	if (!capable(CAP_SYS_ADMIN))
@@ -2065,6 +2916,17 @@
 	return 0;
 }
 
+/**
+ *	fionbio		-	non blocking ioctl
+ *	@file: file to set blocking...
 
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